A genus of c. 150 species, distributed in North temperate regions of both the hemisphere. In Pakistan, it is represented by 21 species.

The genus Persicaria Mill. is sometimes treated in a broader sense and a number of genera like Bistorta, Aconogonon, Rubrivena and Knorringia are included. Most of them are treated here as independent genera on the basis of several characters such as habit, inflorescence, number of stamens and pollen type. In the genus Persicaria (s. str.) two major taxonomic categories can be recognized which probably deserve the rank of two distinct subgenera or even genera. These can be recognized on the basis of the inflorescence and pollen type. In one group the racemes are spike-like cylindrical to filiform and pollen grains are tri to pantoporate whereas in the other group the inflorescence is ovoid or subglobose, capitate, pollen grains are 3-4 colpate. The second group is often placed under a separate section Cephaphilon Meisn. of the genus Polygonum.